Chipotle Mexican Grill’s board is too white, too male and too entrenched, according to an investor group urging shareholders to vote against two directors.

“A board exhibiting low diversity, questionable independence and high tenure is most liable to function as an echo chamber and not as an effective means of differentiated thought leadership or oversight,” said Dieter Waizenegger, executive director of CtW Investment Group in a letter to shareholders on Wednesday.

CtW is calling for shareholders to withhold support for two long-term directors — Patrick Flynn and Darlene Friedman — in advance of the company’s May 11 annual meeting.

It’s not the first time CtW, which works with union-backed pension funds, has agitated for change at Chipotle. In 2014, it urged a revolt against the company’s pay for top executives, with 77 percent of shareholders voting against its compensation programs.

The nine-member board has seven independent directors. The average tenure of the directors is 12.5 years compared with 8.5 years for an S&P 500 company, according to CtW.

“These directors have made hundreds of thousands of dollars, possibly millions, for being directors at Chipotle,” said a spokesman for the D.C.-based group.

“Do they have an undue excessive loyalty to the management team? You do have to question whether the directors can raise credible questions of management.”

In addition to the directors’ longevity, three of the seven outsider directors have strong ties to the Denver and Boulder, Colorado, areas where Chipotle is based “and where co-CEOs Monti Moran and Steve Ells attended college,” Waizenegger said.

The company did not immediately respond to requests for comment.

Shares of Chipotle were down 1.3 percent to $438.95 in early afternoon trading on Wednesday. The stock is off 35 percent over the past year.